This paper explores the potential contributions of modern High-Voltage Direct-Current (HVDC) transmission systems to the Italian National Power System, with a focus on adequacy and security, and providing an overview of their role in system stability. An operational methodology is proposed to assess the impact of planned infrastructure developments, within the context of medium- to long-term forecast scenarios. To this end, starting from a model of the current transmission network, a prospective model of the primary transmission grid for the year 2040 was developed, covering voltage levels of 230 kVAC, 400 kVAC, and 525 kVDC. Load-flow analysis under both N and N-1 conditions was performed, with particular emphasis on the Ionian–Tyrrhenian HVDC backbone “Priolo–Rossano–Latina”.